CN102239748A - Illumination device and method for embedding a data signal in a luminance output using AC driven light sources - Google Patents

Abstract

The invention relates to a lighting device connectable to an alternating voltage source for applying an alternating voltage during a series of time intervals. The lighting device comprises at least a first light source and a second light source arranged to be connected in series to the alternating voltage source so as to produce a light output in response to the alternating voltage. Selection means are provided, configured for selectively applying the alternating voltage to the first light source, or to the first light source and the second light source. A controller is provided for controlling said selection means in response to a data signal comprising data symbols such that one or more of said data symbols are included in said light output. The invention also relates to methods, light receivers and lighting systems for embedding one or more data symbols in the light output of such lighting devices.

Description

Lighting apparatus and method for embedding a data signal in light output using an AC driven light source

technical field

The present invention relates to the field of lighting devices, light receivers, lighting systems and methods, and more particularly to devices, systems and methods for embedding data in the light output of such lighting devices.

Background technique

In recent years, in order to enable consumers to obtain a desired environment for a particular room or space, very advanced lighting systems are being developed.

Examples of such lighting systems are the arrangement of several lighting devices in a structure such as a room, hall or motor vehicle. A lighting device, possibly comprising a light emitting diode, emits visible light carrying a code (series of data symbols), ie coded light, in order to identify a light source or group of light sources. The light source code is transmitted by modulating the light output from the lighting device. In such a lighting system, the light receiver for receiving the code is for example implemented in a remote control device for controlling the lighting device or embedded in another device such as a switch or sensor device.

Coded light is also beneficial for wholesale market luminaires, for example to enable fine tuning of light sources, and allows embedding in the light output individual information representing, for example, temperature or other status information.

Wholesale lighting equipment can have a direct connection between the AC power source and the light source. Such lighting devices generally do not contain electrical drivers. It is believed that such lighting devices pave the way and provide a market for more advanced lighting systems.

Lighting fixtures in which the light source is directly connected to the AC mains have disadvantages compared to DC driven light sources (although these are more expensive), such as lower efficacy and some visible flicker due to the AC modulation frequency.

US2006/175985 discloses a method and circuit for driving light emitting diodes (LEDs) in multiple phases. A string of light emitting diodes is provided, the string of light emitting diodes being divided into groups connected in series with each other. Each group of light emitting diodes is coupled to ground by a separate conductive path. A phase switch is provided in each conductive path. The input voltage is increased so that the string of light emitting diodes is sequentially turned on group by group along the downstream direction of the string of light emitting diodes.

A lighting device comprising such a circuit can be used to switch on/off corresponding LEDs (groups of LEDs) in order to obtain maximum light output, as will be explained in more detail in the detailed description of the figures.

One problem with such AC powered lighting devices is that while the light output can be optimized, it is not possible to embed data symbols (coding) in the light output.

Contents of the invention

It is an object of the present invention to provide an AC driven lighting device, lighting system and method capable of embedding data symbols in the light output. Yet another object of the invention is to provide an optical receiver capable of receiving and processing an optical output containing embedded data.

A lighting device is disclosed which is connectable to an alternating voltage source for applying an alternating voltage during a series of time intervals. The lighting device comprises at least a first light source and a second light source arranged to be connected in series to an alternating voltage source to generate a light output in response to the alternating voltage. Selection means are provided, configured for selectively applying an alternating voltage to the first light source or to the first light source and the second light source. A controller is provided for controlling the selection means in response to a digital signal comprising data symbols such that one or more of the data symbols are included in the light output.

Furthermore, a method of embedding one or more data symbols of a data signal in a light output of a lighting device is disclosed. The lighting device is connected to an alternating voltage source for applying an alternating voltage during a series of time intervals. The lighting device includes at least a first light source and a second light source connected in series with an alternating voltage source for producing a light output in response to an alternating voltage. an alternating voltage responsive to the data signal, the alternating voltage is selectively applied to the first light source or to the first light source and the second light source such that one or more of the data symbols are embedded during a time interval light output.

By selectively controlling selection means, such as a switch, during a time interval, the first light source may be controlled to emit light, or both the first and second light sources may be controlled to emit light. The point in time at which switching occurs during this time interval is called a switching point. The data symbols are embedded in the light output of the lighting device by selectively controlling, ie modulating, the switching point according to the data symbols to be embedded.

It should be noted that binary modulation of the switching points is not necessary. Other types of modulation are also conceivable, including analog modulation (using an amplitude modulated control signal) and digital modulation (comprising multiple levels). The switching point can for example have 4 positions, which allows 2 bits to be included in the light output during a time interval.

It is also to be noted that the disclosed lighting devices are not necessarily applicable for lighting purposes, but also for data communication. As an example, a lighting device may constitute an access point to a network.

Claims 2 and 14 define specific embodiments according to the invention to enable data symbols to be included in the light output. The controller controls the variation of the time switching point between the emission of light from the first light source and the emission of light from both the first light source and the second light source, and thereby determines the duration of the first and second portions of the time interval.

Embodiments of the invention according to claims 3, 4 and 15 allow for differences in switching points between time intervals when the same data symbols are embedded. This dynamic change of the switching point can be applied, for example, in situations where the light receiver is moving relative to the lighting device and the receiver needs to embed data in a higher light output for proper detection of the data signal.

An embodiment of the invention according to claim 5 allows for the use of a simple light receiver capable of detecting a change in light output between two time intervals.

An embodiment of the invention according to claim 6 provides the advantage that there is a substantially constant integrated optical power for successive time intervals and thus avoids significant visible differences in the light output between successive time intervals. flashing.

The embodiments of claims 7 and 8 allow for higher data rates within a certain time interval. The embodiment of claim 7 provides further light sources which can be modulated to embed data symbols in the light output and thus provide further switching points. The embodiment of claim 8 provides repeated selection of the first light source and the corresponding first and second light sources within a time interval.

The embodiment of claim 9 provides a small form factor light source for a lighting device.

In order to be able to retrieve the data symbols from the light output of the lighting device, a light receiver is required. The optical receiver includes an optical detector configured to detect an optical output comprising data symbols. The optical receiver may also include at least one of an integrator and a memory. The integrator is configured to obtain optical power from the detected optical output at each of two time intervals. The memory may store information representing switching points between the first portion and the second portion during a time interval.

The optical receiver also includes a processor. Provided that the optical powers of the different data symbols are substantially equal, eg for the embodiment of claim 6, the processor may be configured to compare only corresponding parts of the two time intervals in order to retrieve the data symbols. Although the optical power may be substantially equal throughout the time interval, various portions of the time interval may represent different optical powers. Data symbols can also be retrieved by comparing detected switch points with stored switch points.

An embodiment of the invention according to claim 12 allows for determining further data from the light source, such as the light intensity received from the lighting device.

Finally, a lighting system is proposed comprising said lighting device and a remote control accommodating such a light receiver.

Embodiments of the present invention will be described in more detail below. However, it should be understood that these examples should not be considered as limiting the protection scope of the present invention.

Description of drawings

In the attached picture:

1 is a schematic diagram of a lighting system installed in a structure according to an embodiment of the present invention;

2A and 2B provide a circuit diagram and a characteristic curve of voltage/brightness for an AC-driven light source;

Figure 3 provides a circuit diagram of a lighting device according to an embodiment of the present invention;

4A and 4B provide light output characteristic curves resulting from a first exemplary method of operating the lighting device of FIG. 3 to embed data symbols;

5A and 5B provide light output characteristic curves resulting from a second exemplary method of operating the lighting device of FIG. 3 to embed data symbols;

Figure 6 is an exemplary embodiment of a lighting device; and

Figure 7 provides a schematic illustration of an optical receiver according to an embodiment of the present invention.

Detailed ways

Figure 1 shows a structure 1, in this case a room, with an installed lighting system 2. The lighting system 2 includes a plurality of lighting devices 3 . The lighting device 3 may comprise a high/low voltage gas discharge source, an inorganic/organic light emitting diode or a laser diode. The lighting system 2 may also comprise a remote control 4 allowing a user to control said lighting device 3 .

Figure 2A provides a circuit diagram of a lighting device 3 connected to an AC voltage source 10 arranged in series with a first light emitting diode (LED) D1 and a second light emitting diode D2. LEDs D1 and D2 emit a light output when a voltage is applied across these LEDs. Light emitting diodes D1 and D2 may represent groups of light emitting diodes. In addition to the respective resistors Rext, Rint and Rshunt, the circuit comprises a rectifier 11 and selection means 12, which are implemented as switches. The switch 12 is arranged in such a way that it can short-circuit the second light-emitting diode D2 in the closed state of the switch. In the embodiment of Figure 2A, this is achieved by providing a tap between LEDs D1 and D2.

FIG. 2B shows the alternating voltage Vmains (left vertical axis) supplied by the alternating voltage source 10 to the LEDs D1 and D2 during a single time interval. Assume that the light emitting diodes D1 and D2 have a threshold voltage Vth of 100 volts. Thus, if switch 12 is open, voltage is applied to the two LEDs D1 and D2 (in series; called string 1 in FIG. 2B ), and light output will only be obtained during periods when the alternating voltage exceeds 200 volts (right side vertical axis). In other words, for a time interval of 0-10 milliseconds, light output is only obtained between 2 and 8 milliseconds. If switch 12 is closed, only an alternating voltage is applied to LED D1 (string 2 in FIG. 2B ), and current will pass through LED D1 at alternating voltages of 100 volts and higher. Thus, the light output of LED D1 starts earlier and goes out later in the time interval than string 1, as shown in Figure 2B. Since string 2 has fewer LEDs, the maximum light output is less than string 1.

The light output of the lighting device 3 can be optimized by switching from string 2 to string 1 at an appropriate point in time (hereinafter also referred to as switching point) using the selection means 12 . The switching points in Fig. 2B are defined such that the entire string (String 1) is selected when the light output of the entire string exceeds the light output of only a part of this string (String 2). In FIG. 2B, switch points are defined at 3 milliseconds and 7 milliseconds. The phase signal shown in FIG. 2A provides the control signal for defining the switching point by operating the selection means 12 and may eg be related to the input voltage.

In an embodiment of the invention, as schematically shown in Fig. 3, a controller 15 is provided for the lighting device 3 in order to manipulate the switching point, compared to the embodiment of Figs. 2A and 2B. In particular, the phase signal for operating switch 12 is modulated by a data signal comprising data symbols to be embedded in the light output of light emitting diodes D1 and D2. The controller 15 may include a receiver 16 for receiving external commands and manipulating data signals in response to such commands. Said receiver 16 can also be used to feed data signals to the controller 15 .

Data symbols can represent various data, such as identification codes or information about (the status of) a particular lighting device. The identifier may comprise a Code Division Multiple Access (CDMA) identifier for uniquely identifying the lighting device 3 in the local environment. Also other schemes are possible, eg the lighting device 3 generates a random identifier of eg 24 bits. As long as the length of the identifier is long enough, the chance of two lighting devices using the same identifier is negligibly small.

It should be noted that the illumination source 3 may also be part of a data communication system, such as a wireless access point.

In general, the data signal will be a binary signal containing only two data symbols "0" and "1" (bits).

4A and 4B illustrate the embedding of data symbols "0" and "1" for the first embodiment. The solid curve represents the actual light output from the lighting device 3, while the extrapolated dashed curve represents the light output of the first and second strings without switching being effected. Obviously, in order to embed a logic "0" in the light output, the controller 15 controls the switch 12 so that an alternating voltage is applied to the LED D1 during the first part of this time interval (between 1 millisecond and 2 milliseconds) and between During the second part of this time interval (between 2 milliseconds and 8 milliseconds) it is applied to LEDs D1 and D2, as shown in Figure 4A. Consequently, a sudden drop in light output is obtained at the switching point due to an increase in the threshold voltage of the light-emitting diodes D1 and D2 provided in series. Another switching point is defined by the data signal at 8 ms, where a sudden rise in light output is obtained. These switching points define a logical "0" in the light output of the lighting device 3 .

Fig. 4B represents the light output of the lighting device 3 when a logical "1" should be embedded. In this case, the controller 15 controls the switch 12 to provide switching points at 3 ms and 7 ms (as opposed to 2 ms and 8 ms for a logic "0" data symbol). In fact, the solid luminance curve in FIG. 4B represents the maximum light output of the lighting device 3 .

It should of course be appreciated that the optical output of Figure 4A could be assigned a logical "1" data symbol, and the optical output of Figure 4B could be assigned a logical "0" data symbol.

The light output characteristic curves shown in FIGS. 4A and 4B using the switched phase mode for the lighting device 3 of FIG. 3 have different integrated light powers and can therefore be easily detected in a light receiver.

The data signal will typically comprise a plurality of data symbols such that the lighting device 3 will produce a plurality of light outputs during successive time intervals as shown in Figures 4A and 4B. When a logical "0" is followed by a logical "1" during a subsequent time interval, or vice versa, the integrated optical power of the light output is varied for successive time intervals. The different optical powers of a logical "0" and a logical "1" can sometimes be experienced visually as a flickering phenomenon of light.

In order to reduce this flicker effect, the optical power difference between the data symbols of the data signal should preferably be kept small. In an embodiment of the invention, this can be achieved by having the controller 15 control the switch 12 in a bi-phase mode, the light output of which is shown in Figures 5A and 5B.

In Fig. 5A, a logic "0" is embedded in the light output of the lighting device 3 by the controller 15 closing the switch 12 at 3 milliseconds and opening the switch 12 at 8 milliseconds during one time interval. On the other hand, as shown in FIG. 5B , a logical "1" is obtained by closing switch 12 at 2 milliseconds and opening switch 12 at 7 milliseconds during the corresponding time interval. By comparing the light output of FIG. 5A and FIG. 5B, it can be observed that the integrated optical power is substantially the same for logic "0" and logic "1", thus reducing the flicker phenomenon.

Again, it should be appreciated that the optical output of Figure 5A may be designated as a logical "1" data symbol, and the optical output of Figure 5B may be designated as a logical "0" data symbol.

It should be noted that in the above-described embodiments, the difference in light output between logic "0" and logic "1" has been exaggerated for clarity.

While the embodiments of Figures 4A, 4B and 5A, 5B illustrate preferred embodiments of the invention, it should be recognized that many additional embodiments exist within the scope of the invention.

As an example, in the above-described embodiment, the controller 15 operates the switch 12 twice within one time interval. However, it is also possible for the switch 12 to be operated once during a time interval, although this is not good for integrating the optical power in a certain time interval. It is also possible that the left and right parts of the light output are modulated separately in order to double the data rate. The first bit is then represented at a first switching point and the second bit is represented at a second switching point. For example, for the first bit, a toggle at 2 milliseconds represents a "0" and a toggle at 3 milliseconds represents a "1". For the second bit, a toggle at 7 milliseconds represents a "0" and a toggle at 8 milliseconds represents a "1". It is also possible for the switch 12 to be operated by the controller 12 three times or more during a time interval in order to embed more data symbols in the light output during a time interval.

In the above-described embodiment, the controller 15 controls the switch 12 so that the switching point is positioned at a place where the light output of a part of the series connection of light-emitting diodes D1, D2 is higher than the light output of the entire series arrangement (in the above-mentioned figures, at intervals 1-3 ms and 7-9 ms). However, in order to increase the switching frequency and correspondingly reduce electromagnetic interference, it may be beneficial to provide a switching point near the midpoint of this time interval.

From FIGS. 4A , 4B and 5A , 5B it can be suggested that a logic “0” and a logic “1” are always represented by the same light output characteristic curve and/or the same switching point. However, this is not necessarily the case. The controller 15 may control the switch 12 to dynamically change the light output characteristic curve and/or the switching point between time intervals while embedding the same data symbols. For example, a logic "0" represented in the light output of FIG. 4A has switching points at 2 milliseconds and 8 milliseconds for the first time interval, but has switching points at 4 milliseconds and 6 milliseconds for subsequent time intervals.

The exemplary embodiment of the lighting device 3 shown in FIG. 3 comprises only two light-emitting diodes D1 , D2 connected in series. It is to be noted that more than two LEDs may be arranged in series, wherein one or more switches 12 are arranged so that an alternating voltage may be selectively applied to one or more LEDs as controlled by the controller 15. superior. This enables embedding of multiple data symbols in the light output of the lighting device 3 within one time interval. Furthermore, the lighting device 3 may comprise several parallel branches with light emitting diodes connected in series.

The modulation of the switching points can be embedded as a small piece of digital logic such as part of a microprocessor in a digital ASIC (Application Specific Integrated Circuit). An embodiment is shown schematically in Figure 6, enabling the switch to not need to switch large currents.

In order to be able to retrieve data symbols from the light output of the lighting device, a light receiver 20 as schematically shown in Fig. 7 can be used. The light receiver 20 comprises a light detector/sensor 21 configured for detecting the light output of the lighting device 3 comprising data symbols. The light receiver 20 also includes a processor 22 .

The optical receiver 20 may further include at least one of an integrator 23 and a memory 24 . Integrator 23 is configured to obtain optical power from the detected optical output at each time interval to identify a "0" or "1" data symbol.

Provided that the optical powers of the different data symbols are substantially equal, with respect to the embodiment of FIGS. The time interval part between milliseconds. Although the optical power is substantially equal throughout the time interval of 0-10 milliseconds, portions of such time intervals may have different optical powers.

Memory 24 may store information representing switching points in light output. The data symbols can be retrieved by comparing the detected switch point with the stored switch point.

Certainly, the memory 24 may also store one or more luminance characteristic curves (or partial luminance characteristic curves) of data symbols for identifying data symbols. The light output can be filtered using characteristic curves and data symbols derived from the filtered results. It is also possible to use the luminance characteristic curve to determine further data from the light source, such as determining light intensity, light color or color temperature from the light received from the lighting device 3 .

The light receiver 20 may be part of a device such as the remote control 4 in FIG. 1 . The remote control 4 or light receiver 20 may comprise means 25 for sending commands to the receiver 16 of the lighting device 3 . For example, the remote control 4 may detect an increase in the distance between the remote control and the lighting device 3 and then command the lighting device 3 to move the switching point to a higher light output in order to continue proper reception of data symbols.

Claims (15)

1. lighting apparatus, can be connected to alternating-current voltage source, described alternating-current voltage source was used for applying alternating voltage during a series of time interval, described lighting apparatus comprises first light source and secondary light source at least, described first light source and described secondary light source are arranged to be connected in series to described alternating-current voltage source and produce light output to respond described alternating voltage, described lighting apparatus also comprises choice device and controller, described choice device is used for optionally being applied to described alternating voltage on described first light source or being applied to described first light source and described secondary light source, and described controller is disposed for responding that the data-signal that comprises data symbol is controlled described choice device so that comprise one or more data symbols of described data symbol in the output of described light.

2. lighting device according to claim 1, wherein said choice device is configured to applying described alternating voltage during the first at least in one of described time interval on described first light source, and applying described alternating voltage during the second portion in one of described time interval on described first light source and described secondary light source, wherein said controller is disposed for changing the duration of described first and described second portion between at least two time intervals in the described a series of time interval.

3. lighting apparatus according to claim 2, wherein said data-signal is the binary signal that comprises first data symbol and second data symbol, and wherein said controller is suitable for dynamically changing the described duration of described first and described second portion, so that transmit the described data symbol of described binary signal in the described light output between described two time intervals.

4. lighting apparatus according to claim 3 also comprises receiver, and described receiver is connected to described controller, and is disposed for receiving the command signal that is used for dynamically changing the described duration.

5. lighting apparatus according to claim 2, wherein said controller be disposed in described two time intervals the very first time at interval and change duration of described first and described second portion between second time interval in described two time intervals so that the described light output of described lighting apparatus for different data symbols described very first time in described two time intervals at interval and different between described second time interval.

6. lighting apparatus according to claim 2, wherein said modulating device be disposed for very first time in described two time intervals at interval and change described duration of described first and described second portion between second time interval in described two time intervals so that the described light output of described lighting apparatus keeps constant for different data symbols at interval and between described second time interval basically in the described very first time in described two time intervals.

7. lighting apparatus according to claim 1, at least also comprise the 3rd light source, described the 3rd light source is connected in series to described first light source and described secondary light source, so that responding described alternating voltage makes contributions to described light output, the described choice device that wherein is used to apply described alternating voltage also is disposed for optionally applying described alternating voltage on described the 3rd light source, and wherein said controller is disposed for controlling described choice device and optionally applies described alternating voltage so that respond described data-signal on described the 3rd light source.

8. lighting apparatus according to claim 1, wherein said controller is disposed for controlling described choice device, so that optionally apply described alternating voltage, so that described alternating voltage is being applied on described first light source during two or more parts in the single time interval to described first light source and described secondary light source.

9. lighting apparatus according to claim 1, wherein said first light source and described secondary light source comprise light-emitting diode.

10. an optical receiver is configured to use with lighting apparatus according to claim 2, and wherein said receiver comprises:

-photodetector is disposed for detecting the described light output that comprises described data symbol; And in the following stated parts at least one:

-integrator is used for obtaining luminous power for each time interval in described two time intervals from the light output of described detection;

-memory, the described first of storage representation during a described time interval and the information of the switching point between the described second portion at least;

Wherein said optical receiver also comprises:

-processor, be disposed for perhaps being disposed for according to the light output of described detection and the described data symbol of relatively acquisition of described canned data according to obtaining described data symbol from the optical power difference of described integrator based on the appropriate section in described two time intervals.

11. optical receiver according to claim 10, wherein said data-signal is the binary signal that comprises first symbol and second symbol, and at least one light output that wherein said memory also is included at least one symbol during a described time interval, in described first symbol of representative and described second symbol distributes.

12. an illuminator comprises one or more lighting apparatus according to claim 1 and remote controller, described remote controller comprises at least one optical receiver according to claim 10, and described lighting apparatus is configured to use described remote controller to control.

13. method that in the light output of lighting apparatus, embeds one or more data symbols of data-signal, described lighting apparatus can be connected to alternating-current voltage source, described alternating-current voltage source was used for applying alternating voltage during a series of time interval, described lighting apparatus comprises first light source and secondary light source at least, described first light source and described secondary light source and described alternating-current voltage source are connected in series and produce described light output to respond described alternating voltage, described method comprises the steps: to respond described data-signal and is optionally applying described alternating voltage on described first light source or on described first light source and described secondary light source, so that embed one or more data symbols of described data symbol in described light output.

14. method according to claim 13 comprises the steps:

During-the first at least in a time interval in the described time interval, on described first light source, apply described alternating voltage;

During-the second portion in a described time interval in the described time interval, on described first light source and described secondary light source, apply described alternating voltage;

-between at least two time intervals in the described a series of time interval, the duration that changes the described first in the described time interval and described second portion is so that embed described data-signal.

15. method according to claim 14, wherein said lighting apparatus also comprises receiver, and described data-signal is the signal that comprises first data symbol and second data symbol, and described method also comprises the steps:

-in described receiver place reception command signal;

-dynamically change the described duration of described first and described second portion, so that between described two time intervals, transmit the described data symbol of described signal.

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